Microbiology Exam #3Ch. 13 Review

Antisepsis

Antimicrobial chemical, safe for skin - Hydrogen peroxide, isopropyl alcohol

Microbial death curve

Bacterial populations die at a constant log. rate in %

Alkylating agents - β-Propionolactone

Binds to DNA, inactivating it; clear liquid w. strong odor has the ability to kill endospores. - Use in sterilization for medical instruments and tissue graft as well as blood plasma, milk, and water.

Milk borne organism killed by pasteurization:

C.jejuni, Coxiella burnetii, Listeria monocytogenes, E. coli O157:H7, M. tuberculosis, M. paratuberculosis, Salmonella spp. and Yersinia enterocolitica

Halogens:

Chemicals commonly used for disinfection iodine, Chlorine, Fluorine

High-efficiency particulate air (HEPA) filters

filters a variety of applications and used widely in clinical settings, cars, airplanes, and even at home.

Autoclave:

high heat and pressure to sterilize items eliminating veg cells viruses, and endospores. Works by: removing the air inside the chamber w. ↑ amount steam which bulbs pressure and temp. to sterilize the items inside (20min depends on vol.). After the steam is released, pressure ↓, its chamber can be opened. 1. Record - document the pressure and temp of each run 2. Autoclave tape- color change for appropriate Temp is used 3. Spore test- length of exposures.

-static:

inactivate growth

Disinfection

inactivation/kills most microbes on the surface of a fomite (Inanimate items that harbor microbes and aid in transmission) - Fast acting, easy to use, products like vinegar or bleach, but not completely sterile.

Disinfection/Antisepsis

inactive and destroy microbes

Peroxygens - Carbamide peroxide

ingredient in toothpaste, combats oral biofilms cause tooth discoloration and halitosis (bad breath).

Propionic acid

inhibit enzymes and ↓ intracellular pH, more effective preservative at a higher pH than either sorbic or benzoic acid. - It is naturally produced by some cheeses and is added to other types of baked goods to prevent mold contamination. - It is also added to raw dough to prevent contamination by B. mesentericus, which causes bread to become ropy.

Natamycin

is an antifungal macrolide antibiotic produced by Streptomyces natalensis. - It's used to prevent fungal growth in various types of dairy products, including cheese.

Peroxygens - Benzoyl peroxide

is used in acne medication solutions. It kills the bacterium Propionibacterium acnes.

Disinfectant/ preservative testing: Low-level

kill only vegetative cells and certain enveloped viruses, and are ineffective against endospores.

Refrigeration

lab or home (temp range 0°C-7°C.), slows microbial growth and help pressure products for food or medical supplies

Disinfectant/ preservative testing: Intermediate-level

less effective against endospores and certain viruses

Peroxygens - Peracetic acid

which is more effective than hydrogen peroxide, is immune to inactivation by catalases & peroxidases. However, it can be more irritating and demanding to the skin and shouldn't be used as an antiseptic.

Peroxygens - Hydrogen peroxide

widely used, often used to disinfect surfaces, and may be used as a gaseous agent. - Work against gram(+/-) bacteria such as fungi, viruses, and endospores, However, bacteria that produce the oxygen-detoxifying enzymes, like catalase or peroxidase, have inherent tolerance to low hydrogen peroxide concentrations.

Sorbic acid

work by inhibiting various cellular enzymes (citric acid cycle, as well as catalase and peroxidase) - ↑ efficacy as pH ↓ - It is added to a wide variety of foods, including dairy, bread, fruit, and vegetable products.

Halogens - Iodine

works by oxidizing cellular components, like amino acids, nucleotides, and fatty acids iodophor is an organic molecule, commonly used as a hand scrub by medical personnel before surgery and for topical antisepsis of a patient's skin before incision.

Heavy metals - Nickels and zinc

zinc chloride - found in mouthwashes. Zinc oxide - found in topical antiseptic creams such as calamine lotion, diaper ointments, baby powder, and dandruff shampoos.

Sanitization/Degerming

↓ the microbial load. (abundance ↓ to the level that won't affect humans too bad)

Benzoic acid

↓intracellular pH, interfering with mechanisms such as oxidative phosphorylation and uptake of amino acids. - Founds naturally in fruit juices, jams, ice creams, pastries, soft drinks, chewing gum, and pickles.

Freezing

-2°C may stop microbial growth and even kill susceptible organisms. - If medical specimens require long-term storage or transport are often frozen at -70°C or ↓.

Phenolics

Compounds of a benzene ring with an -OH group, and they can be found naturally in plants or derived from a component of coal tar. They inhibit microbial growth by denaturing proteins and disrupting membranes. - Carbolic acid - first chemical that scientists began experimenting with as a disinfectant. It was first used during use by joseph lister as a disinfectant for the treatment of surgical wounds - Lysol - used as active ingredient in various formulation - Triclosan - used in many antibacterial products, like toothpaste and hand soaps, but banned by FDA as it was shown to be detrimental to humans.

BSL-4:

Dangerous and fatal; exotics and easily transmitted infection (no treatment); 13labs only (u.s) - Ebola, Marburg, smallpox. - They need to change, shower, and decontaminate all material. Lab must be in an isolated location, with its own exhaust system. - Work in a biological safety cabinet with a high-efficiency particulate air (HEPA)-filtered at all times

The application of high pressure kills vegetative cells by protein denaturation, but endospores may survive.

Ex: Clostridium botulinum - they can contaminate home canned endospores and survive if it was done with boiling water instead of pressure.

2 types of air removal

Gravity: steam is used to push out air Prevacuum: air is removed then stream is introduced in the chamber.

Halogens - Chlorine

Hypochlorous acid - used in municipal drinking water and wastewater treatment plants Sodium hypochlorite - bleach Chloramine - They are derivatives of ammonia by substituting 1, 2, or all 3 hydrogen atoms w chlorine atoms. - (swimming pool's smell) the pool isn't properly chlorinated. It's mixed with urine, feces, or other bodily fluids. - disadvantages: irritate the skin, nose, or eyes and they may not completely eliminate certain hardy organisms.

gamma & x-rays

Ionizing radiation commonly used to sterilize materials that cannot be autoclaved, such as plastic. - In Europe, gamma irradiation for food preservation is widely used.

-cidal:

Kill

Thermal death point (TDP):

Lowest temp. at which all microbes are killed in a 10min exposure

Heavy metals

MOA: Binds to & inhibits proteins; not selectively toxic to microbial cells. They may bioaccumulate in human or animal cells, and excessive concentrations can have toxic effects on humans (argyria - too much silver accumulates in the body, turning the skin blue-gray)

BSL-2:

Moderate risk, "indigenous"- commonly found in that area, restored accesses - Restricted access; additional PPE including face shield, eyewash station and autoclaves - S. aureus and Salmonella spp., or viruses: hep., mumps, and measles viruses. - Aerosolization - biological safety cabinets for procedures that may disperse agents though the air.

In clinical settings, hyperbaric oxygen therapy is sometimes used to treat infections.

Patient is supplied oxygen through a breathing tube. They breathe in pure O2 at a pressure higher than normal atmospheric. This ↑ oxygen saturation causes tissue to become hypoxic due to infection and inflammation.

Surfactants

Surface-active agents: a group of chemical compounds that ↓ the surface tension of water. The major ingredient in soaps and detergents. (both have polar/nonpolar regions, help create emulsion in water, taking away dirt from skin surfaces) 1. Soaps - no-kill of microbes but carries them away. 2. Detergents - synthetic surfactant molecules with both polar and nonpolar regions.

Decimal reduction time (DRT) or D-value

The amount of time it takes for a specific protocol to kill one order of magnitude of microbes or 90% of the population

Ionizing radiation

X-rays, gamma rays, and high-energy electron beams. It is strong enough to pass into the cell, alters molecular structures, and damages cell components.

Pasteurization

a form of microbial control the uses heat but doesn't render it sterile eventually; kills pathogens and reduces the # of spoilages-causing microbes while making quality

Anionic

a negatively charged anion at one end attached to a long hydrophobic chain

Halogens - Fluorine

antimicrobial halogen that helps prevent dental caries (cavities).

Nisin

antimicrobial peptide produced by Lactococcus lactis and effective against gram(+) organisms. - It works by disrupting cell wall production, leaving cells more prone to lysis. - It is used to preserve cheeses, meats, and beverages.

Dry-heat:

aseptic tech. In lab typically using direct application of high heat, (inoculating loop) - Last long period of time like 2 hrs. (oven)

Bisbiguanides

cationic (positively charged) molecules known for their antiseptic properties. - It works against enveloped viruses, not as effective against non-enveloped viruses (M. tuberculosis), and is not sporicidal.

Phenol coefficient

chemical agent's effectiveness often compared to phenol. (test subject, S. aureus, and Salmonella enterica. was diluted in water for 7.5 minutes) 1. Coefficient =1.0 same level of effectiveness as phenol. 2. Coefficient <1.0 is less effective than phenol. 3. Coefficient >1.0 is more effective than phenol

Noncritical:

clean but not highly disinfect (do not penetrate the skin) Ex: Bedlinen, stethoscopes, blood pressure cuffs, etc

Bisbiguanides - Chlorhexidine

common surgical and longer-lasting than iodophors.

Sterilization

complete removal or killing of all veg. Cells, endospores, viruses - Used in the lab, medical, manufacturing and food industry. - Used heat, pressure, filtration, and chemical (achieve sterilization are called sterilant)

Critical:

completely sterile (often penetrate tissue or bloodstreams) Ex: Surgical equipment, catheter, Iv fluids

Alkylating agents - Formaldehyde

cross-links proteins and has been widely used as a chemical fixative.

In-Use test

determine an actively used solution of disinfectant is contaminated. To performed this test: 1. A 1-mL sample is diluted into a 9 mL solution broth medium that also contains a compound to inactivate the disinfectant. 2. 200 microliter is then taken from the broth and is inoculated onto each of the 2 agar plates. 3. 1 plate is incubated at 37°C for 3 days and the other is incubated at room temp. for 7 days. 4. The growth of 5+ colonies suggests that viable microbial cells in the disinfectant solution are contaminated.

Use-dilution

determine disinfection effectiveness on an inanimate surface. For this test: 1. Stainless steel Cylinders dipped in targeted culture and dried. 2. The cylinder is then dipped into various concentrations of disinfectant. 3. Finally, the cylinder is transferred to a new test tube containing a fresh sterile medium. 4. After incubation, the tubes were then observed for microbial growth. - Turbidity = bacterial growth, No Turbidity = Organism killed

Desiccation

drying or dehydration to preserve foods; effective because microbes need water to survive, but endospores might not be killed, so it will grow again in a favorable condition.

Biological Safety level (BSL):

established by: CDC, NIH, & WHO - CDC determines the BSL on the agent's infectivity, ease of transmission, and potential severity, type of work being done.

High-temp short-time:

expose milk to 72℃ for 15 sec. This lowers bacterial numbers while preserving the quality of the milk.

Ultra-high-temp:

exposes milk to 138℃ for 2 or more sec. These milks can be stored for a long time in a sealed container without being refrigerated.

Pascalization

exposure to high pressure kills many microbes like bacteria, yeast, molds, parasites, & viruses in foods while maintaining quality & extending shelf life.

Bisbiguanides - Alexidine

gaining popularity as a surgical scrub and an oral rinse because it acts faster than chlorhexidine

Alkylating agents - Ethylene oxide

gaseous sterilization that has a high penetrating ability and can sterilize items within plastic bags such as catheters, disposable items in laboratories and clinical settings. - Its exposure is a form of cold sterilization, making it useful for the sterilization of heat-sensitive items.

Disinfectant/ preservative testing: High-level

have the ability to kill vegetative cells, fungi, viruses, and endospores, leading to sterilization, with extended use.

BSL-3:

lethal infection by inhalation, indigenous or exotic; M. tuberculosis, B. anthracis, West Nile virus, and HIV. - Also wear respirator, and work in Aerosolization all the time. - Hand-free sink, eye wash, 2 set of self closing door, - Directional air flow-clean air pulled into the lab isn't recirculated

Water activity

lowered without physical drying by adding solutes (salts or sugars). - When added in, microbial cells are reduced because water will be drawn from an area of low solute concentration (inside the cell) to an area of high solute concentration (outside the cell) where all the salts and sugars are at.

Disk diffusion

measures degree of inhibition using sterile filter paper disks with chemicals - The chemicals diffuse out of the disks into the agar after the plates have been inoculated and the "lawn" of bacteria grows, zones of inhibition of microbial growth are observed as clear areas around the disks. - The larger zones of inhibition the more effective that agent is against the microbes. The closer the microbe grows to the disk the more resistant to the agent they are.

Filtration

method of physically separating microbes from samples.

Moist-heat:

more effective protocol (penetrates cells better) - Boiling is not considered a good sterilization

BSL-1:

no harm, ex: E. coli and B. subtilis (infect animals) - Labs: standard aseptic technique, lab coat, goggle, gloves

Peroxygens

oxidizing agents used as disinfectants or antiseptics, producing free radicals that damage cellular macromolecules.

Membrane filtration

pore size of 0.2 µm which is smaller than the average bacteria (1 µm). Useful for removing microbes from heat-sensitive solutions (antibiotics and vitamins solutions).

Cation

positively changed; important class of disinfectants and antiseptics called: quaternary ammonium salts (quats)

Aseptic technique

prevent contamination on item, person and environment.

Sulfur dioxide:

prevents browning of foods and is used for the preservation of dried fruits; it has been used in winemaking since ancient times. - dissolves in water readily, forming sulfites.

Lyophilization

rapidly frozen (snap-frozen) and placed under vacuum; effective as it combiens cold temp and discussion, causing less damage to items and better preserved.

Sanitation

reduce microbial load on fomite; done with heat or chemical - Use in dishwasher (commercial/industrial) or hospital disinfectant

Degerming

reducing microbial # when gently scrubbing living tissue; use of mild chemical - Hand washing

Semicritical:

require high levels of disinfection (not sterile) (contact mucus membranes or non-intact skin) Ex: Gastrointestinal endoscope, respiratory therapy equipment.

Alkylating agents - Glutaraldehyde

similar to formaldehyde but has two reactive aldehyde groups, allowing it to act more quickly. - It is used to disinfect a variety of surfaces and surgical and medical equipment.

Alkylating agents

strong disinfecting chemicals that act by replacing a hydrogen atom within a molecule with an alkyl group, MOA: inactivating enzymes and nucleic acids.

Supercritical fluid

temperature and pressure ↑, reaches a supercritical state that has physical properties between liquids and gases. - Materials put into a chamber this way can be sterilized because of the ability of scCO2 to penetrate surfaces, Forming carbonic acid, which↓cell pH. It's nonreactive, nontoxic, and nonflammable. It's good for use on vulnerable items such as some food and tissue.

Heavy metals - Mercury

treated syphilis but banned b/c of neural toxicity effects

Heavy metals - Silver

treats topical wounds and prevents infection; Silver nitrate drops were once used to treat pediatric ophthalmia Neonatorum; commonly incorporated into catheters and bandages making them antimicrobial.

Sonication:

use of high-frequency ultrasound waves to disrupt cell structures (leading to lysis) - rapid changes in pressure within the intracellular liquid leads to cavitation (formation of bubbles inside the cell). Ex: Cleaning surgical instruments, lenses, and a variety of other objects such as coins, tools, and musical instruments.

Heavy metals - Copper Sulfate

used as algicide to treat pools

Alcohols

used as disinfectants and antiseptics; MOA: denaturing proteins and by disrupting membranes, leads to cell lysis. - used at concentrations of about 70% - coagulate proteins - bactericidal and fungicidal, but may also be virucidal for enveloped viruses only; used combo with iodine

Non-ionizing

used for sterilization and uses less energy, however it does not penetrate cells or packaging Ex: UV light causes thymine dimers to form between adjacent thymines within a single strand of DNA. This leads to formation of mutations that can ultimately kill microorganisms.

Peroxygens - Ozone gas

used to clean air or water supplies.

Thermal death time (TDT):

The length of time needed to kill all microbes in a sample at a given temp.

Nitrates

They reduce to nitric oxide, which reacts with iron-sulfur groups. This destroys the ETC and prevents ATP synthesis. - Added to processed meats to maintain color and stop the germination of C. botulinum endospores. - Nitrosamines (carcinogenic) and produced through exposure to nitrite-preserved meats during cooking.